The present invention relates generally to a method and apparatus for performing tests to determine the ductility of welds. Specifically, the test method is carried out using an apparatus to operate upon a metallic weld test specimen by subjecting the specimen, in the vicinity of the weld, to a bending force.
It is frequently desirable or necessary to test the ductility of a weld joining two pieces of similar or dissimilar metallic materials. For example, as a product is being designed that will require welding for its assembly, the characteristics and performance of particular materials and welding techniques may be tested to ensure that they possess adequate ductility in conformance with applicable codes or standards. As another example, training an individual in welding techniques or determining the individual's welding skill can be facilitated by testing the ductility of welds made.
Bend testing has been widely used in the welding industry for the purposes noted above. In performing such tests, a sample is made by welding two plates or pipes together in end-to-end fashion. Single bar specimens are then cut from the sample in such a way that the weld is positioned either transversely or longitudinally to the length of the specimen. The test is then performed by attempting to bend the specimen through 180.degree. about a given radius. The extent to which the specimen may be bent without breaking along the weld is indicative of the weld ductility. An acceptable weld will be capable of being fully bent, although other defects present in the weld may be identified by examination of the bent specimen.
A known device for performing a wrap-around bend test is shown in U.S. Pat. No. 3,906,784, issued Sept. 23, 1975 to Coulstring. A clamp is positioned on a horizontal base with one end of the test specimen being secured in the clamp. A roller pair assembly, with the rollers having parallel axes of rotation, is mounted to the base with the axes extending vertically from the base. The roller pair assembly is further mounted for rotational movement around one of the roller pair axes. The position of the other roller is adjustable, so that after one end of the specimen is clamped in place, the welded portion may be positioned between the rollers with the rollers in contact with the specimen. The roller assembly is then rotated, with the one roller bending the specimen about the other.
By requiring a horizontal surface on which the test is carried out, the Coulstring apparatus represents a rather bulky piece of equipment. Further, during the bending operation, the sample will be subject to forces tending to pull it from the clamp attached to one end of the sample. Thus, the clamping mechanism must be capable of significant clamping force which must be carefully and firmly applied.
A second type of guided bend test may be performed by supporting the specimen in a horizontal orientation at its ends. A mandrel is lowered into contact with the central portion of the specimen, and force is applied to the specimen to cause it to bend. It may be desirable to perform both wrap-around and mandrel-type guided bend tests at the same location. In such cases it would be particularly desirable to utilize a wrap-around test apparatus which could form an attachment for an overhead-type guided bend test apparatus.
What is needed therefore, is an improved wrap-around bend test apparatus which can be made relatively compact and of relatively simple design and operation. If desired, the bend test apparatus should be capable of configuration as an attachment to other bend test equipment.